The invention relates to an apparatus for finish rolling or smoothing crankshaft bearing seats by means of cylindrical rolling tools. The rolling tools are supported on the one hand at the crankshaft bearing seat and on the other hand at each of the circumferential surfaces of two large idler rollers situated side by side. The rolling tools may be provided with contoured radii at the transition zone from the cylindrical surface area to the base surfaces of the rolling tools or tool rollers.
Finish rolling devices of this type are described in U.S. Pat. No. 3,735,620. Such devices have, in addition to cylindrical rolling tools, opposingly arranged frustum cone-shaped rolling tools which bear axially against the surfaces of the transition radii, whereby the entire apparatus is provided with a stable guide. Apparatuses of this type have been proven to be most useful for machining of crankshaft bearing seats with tangential radii transitions because a contacting of the axial guiding surfaces of the crankshaft bearing seats is prevented by the frustum guide rollers.
However, in crankshaft bearing seats in which the radii transitions are not tangential, but rather radially and/or axially grooved by plunge cutting, the disadvantage occurs that the rolling tools may no longer be supported at the surfaces of the radii transitions. Rather, the facing ends of the rolling tools bear against the axial guiding surfaces of the crankshaft bearing seats thereby damaging the bearing seats and thus rendering the work piece being machined totally unusable.
The exclusive use of cylindrically shaped rollers is necessary in order to avoid axial sliding. Such sliding necessarily occurs where frustum cone-shaped rolling tools are used. Such sliding may be desirable when machining crankshaft bearing seats with tangential radii transitions. Otherwise, such axial sliding must be avoided. It appears, however, that the idler rollers and the rolling tools cannot be made absolutely cylindrical, nor can the axes of the rollers be set absolutely parallel to one another due to unavoidable inaccuracies or machining tolerances. Thus, an axial movement of the rolling tools and of the idler rollers may occur in respective opposite directions due to the roll motion of the rolling tools on the work piece. Due to this axial movement the tool housing on the one hand, and the base surface of the cylindrical tool roller on the other hand run against the respective axial guide surfaces of the crankshaft bearing seats whereby the above mentioned damages to the axial guide surfaces of the crankshaft bearing seats are caused.